This is a note to let you know that I've just added the patch titled
perf stat: Fix handling of --for-each-cgroup with --bpf-counters to match non BPF mode
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
perf-stat-fix-handling-of-for-each-cgroup-with-bpf-c.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 6b9bb3f100db7ed53486c9bd8e7fe7d867a423f6
Author: Namhyung Kim <namhyung@xxxxxxxxxx>
Date: Tue Jan 3 22:44:02 2023 -0800
perf stat: Fix handling of --for-each-cgroup with --bpf-counters to match non BPF mode
[ Upstream commit 54b353a20c7e8be98414754f5aff98c8a68fcc1f ]
The --for-each-cgroup can have the same cgroup multiple times, but this
confuses BPF counters (since they have the same cgroup id), making only
the last cgroup events to be counted.
Let's check the cgroup name before adding a new entry to the cgroups
list.
Before:
$ sudo ./perf stat -a --bpf-counters --for-each-cgroup /,/ sleep 1
Performance counter stats for 'system wide':
<not counted> msec cpu-clock /
<not counted> context-switches /
<not counted> cpu-migrations /
<not counted> page-faults /
<not counted> cycles /
<not counted> instructions /
<not counted> branches /
<not counted> branch-misses /
8,016.04 msec cpu-clock / # 7.998 CPUs utilized
6,152 context-switches / # 767.461 /sec
250 cpu-migrations / # 31.187 /sec
442 page-faults / # 55.139 /sec
613,111,487 cycles / # 0.076 GHz
280,599,604 instructions / # 0.46 insn per cycle
57,692,724 branches / # 7.197 M/sec
3,385,168 branch-misses / # 5.87% of all branches
1.002220125 seconds time elapsed
After it becomes similar to the non-BPF mode:
$ sudo ./perf stat -a --bpf-counters --for-each-cgroup /,/ sleep 1
Performance counter stats for 'system wide':
8,013.38 msec cpu-clock / # 7.998 CPUs utilized
6,859 context-switches / # 855.944 /sec
334 cpu-migrations / # 41.680 /sec
345 page-faults / # 43.053 /sec
782,326,119 cycles / # 0.098 GHz
471,645,724 instructions / # 0.60 insn per cycle
94,963,430 branches / # 11.851 M/sec
3,685,511 branch-misses / # 3.88% of all branches
1.001864539 seconds time elapsed
Committer notes:
As a reminder, to test with BPF counters one has to use BUILD_BPF_SKEL=1
in the make command line and have clang/llvm installed when building
perf, otherwise the --bpf-counters option will not be available:
# perf stat -a --bpf-counters --for-each-cgroup /,/ sleep 1
Error: unknown option `bpf-counters'
Usage: perf stat [<options>] [<command>]
-a, --all-cpus system-wide collection from all CPUs
<SNIP>
#
Fixes: bb1c15b60b981d10 ("perf stat: Support regex pattern in --for-each-cgroup")
Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx>
Tested-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Cc: bpf@xxxxxxxxxxxxxxx
Cc: Ian Rogers <irogers@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Song Liu <songliubraving@xxxxxx>
Link: https://lore.kernel.org/r/20230104064402.1551516-5-namhyung@xxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/tools/perf/util/cgroup.c b/tools/perf/util/cgroup.c
index e99b41f9be45..cd978c240e0d 100644
--- a/tools/perf/util/cgroup.c
+++ b/tools/perf/util/cgroup.c
@@ -224,6 +224,19 @@ static int add_cgroup_name(const char *fpath, const struct stat *sb __maybe_unus
return 0;
}
+static int check_and_add_cgroup_name(const char *fpath)
+{
+ struct cgroup_name *cn;
+
+ list_for_each_entry(cn, &cgroup_list, list) {
+ if (!strcmp(cn->name, fpath))
+ return 0;
+ }
+
+ /* pretend if it's added by ftw() */
+ return add_cgroup_name(fpath, NULL, FTW_D, NULL);
+}
+
static void release_cgroup_list(void)
{
struct cgroup_name *cn;
@@ -242,7 +255,7 @@ static int list_cgroups(const char *str)
struct cgroup_name *cn;
char *s;
- /* use given name as is - for testing purpose */
+ /* use given name as is when no regex is given */
for (;;) {
p = strchr(str, ',');
e = p ? p : eos;
@@ -253,13 +266,13 @@ static int list_cgroups(const char *str)
s = strndup(str, e - str);
if (!s)
return -1;
- /* pretend if it's added by ftw() */
- ret = add_cgroup_name(s, NULL, FTW_D, NULL);
+
+ ret = check_and_add_cgroup_name(s);
free(s);
- if (ret)
+ if (ret < 0)
return -1;
} else {
- if (add_cgroup_name("", NULL, FTW_D, NULL) < 0)
+ if (check_and_add_cgroup_name("/") < 0)
return -1;
}
